a(n) = T(n,1), array T as in A054134.

Terms

a(0) =2a(1) =4a(2) =9a(3) =19a(4) =39a(5) =79a(6) =159a(7) =319a(8) =639a(9) =1279a(10) =2559a(11) =5119a(12) =10239a(13) =20479a(14) =40959a(15) =81919a(16) =163839a(17) =327679a(18) =655359a(19) =1310719a(20) =2621439a(21) =5242879a(22) =10485759a(23) =20971519a(24) =41943039a(25) =83886079a(26) =167772159a(27) =335544319a(28) =671088639a(29) =1342177279